Alcohol Use and HIV Risk in the iPrEx Study

Thesis (Master's)--University of Washington, 2015Introduction: HIV acquisition continues to be a critical global health concern even with existing effective prevention strategies. Men who have sex with men (MSM) are disproportionately affected by the epidemic. Unhealthy alcohol consumption is prevalent in certain MSM populations and has been shown to be a risk factor for HIV infection. The objective of this study is to describe the association between unhealthy alcohol use over time and HIV acquisition in the iPrEx (Pre-exposure Prophylaxis Initiative) study, which was an HIV pre-exposure prophylaxis (PrEP) trial in MSM enrolled in 6 countries. Methods: Data for this study were obtained from the iPrEx study, which was a phase III, randomized placebo-controlled trial that evaluated the safety and efficacy of daily, oral FTC/TDF for HIV PrEP in initially HIV-uninfected MSM. Alcohol use and sex behavior data were collected quarterly throughout follow-up and HIV laboratory assays were performed monthly. Cox proportional hazards models were used to assess the association between time-varying average volume of alcohol consumed and HIV acquisition. The Cox models were sequentially adjusted in order to ensure adequate control for measured confounders. Results: The analytical sample included 2,361 participants of whom 139 became HIV infected during the study. The mean age of the sample was 27 years old, and the range of follow-up time was between 3 months and 3.3 years (median = 1.8). At baseline, the majority of the cohort reported drinking (87%), and over half reported typically drinking 1-4 drinks or 5 or more drinks (52%). There was a positive, but not statistically significant association between HIV acquisition and reporting an average of 1-4 drinks or 5 or more drinks, relative to no drinking, in all of the models. There was a significant association between sharing large bottles/pitchers of beer and HIV acquisition compared to not drinking alcohol in the model adjusting for site and treatment assignment, (adjusted hazard ratio [AHR] 2.01, 95% CI: 1.03, 3.90); however, this finding was no longer significant after further adjustment for demographic characteristics and sex behavior (AHR 1.83, 95% CI: 0.94, 3.56). Conclusions: In this diverse but select cohort of MSM, we did not observe a statistically significant association between average volume of drinking and HIV acquisition. In the model only adjusted for site and treatment assignment we did find a significant association between reporting sharing of bottles/pitchers of beer. While this association was attenuated after adjustment for additional demographic and behavioral characteristics, findings related to shared bottles/pitchers are hypothesis-generating and may warrant further investigation